Traverse mechanism



y 6, 1965 s. B. SEAR ETAL 07 TRAVERSE ME CHAN I SM Filed Sept. 11,1963

ZAI MM ATTORNEYS United States Patent Office ddhdfid? Patented July 6, 1965 3,193,297 TRAVERSE MEQHANldh i Stuart Bernard dear and Raymond Holden Speakman,

Harrogate, England, assignors to imperial Chemical Industries Limited, London, England, a corporation of Great Britain.

Filed Sept. 11, 1963, Ser. No. 308,153 4 Claims. ({Zl. 242-43) This invention relates to a traverse mechanism and in particular to a traverse mechanism for use as part of a high speed yarn winding means.

In winding yarn onto packages in the form of cheeses (cylindrical packages) or cones it is necessary to pass the yarn through a guide which reciprocates in close proximity to the package. For winding cheeses and some types of cones it is required that the guide should travel as nearly as possible at constant linear speed across the package face and reverse in direction as nearly instantaneously as possible at the ends of the package. For some types of come the linear velocity of the guide is required to vary to a small extent in traversing from one end of the cone to the other, but the same requirement of as nearly as possible instantaneous reversal at the package ends still applies.

In practice, because of the finite weight of the traverse guide and any mountingbar which may be reciprocating with it, completely instantaneous reversal cannot be achieved since this would demand infinite deceleration and hence infinite forces which would break the mechanism. A compromise must, therefore, be adopted in which the change in velocity occurs within a reasonably short time, such that the forces of deceleration and acceleration are limited to those which the mechanism can accept without fracture or undue wear.

One commonly adopted mechanism comprises a cylindrical cam in which a groove has been cut to guide a roller or peg follower, the latter being connected with the yarn guide usually by means of a rigid rod or tube known as the traverse bar. The groove in the cam is arranged to give the required velocity changes to the traversing parts and the cam and its follower, together with the traversing parts, are made as robustly as possible, the latter also being as light in weight as possible so that the reversal forces do not result in damage or excessive wear to the equipment.

' This system can be satisfactory, if carefully designed, at traverse rates up to about 400 cycles per minute, but even at this speed appreciable sacrifice in speed of reversal must be accepted if long life is needed and the result is that packages suffering from the well known defect of hard ends tend to be produced.

Modern processing developments, especially of synthetic fibres, are demanding increasingly high winding speeds, and this limitation to about 400 cycles per minute limits the maximum winding speed to the region of 4,0005,000 ft./min. though the actual limit is determined somewhat by the type of yarn being wound.

Various alternative traverse systems are known, for example, the split drum traverse roll described in British patent specification 874,651 in which the yarn alone is reciprocated thereby effectively avoiding the inertia forces of reversal. This system, however, has certain inherent limitations such as a tendency to damage the yarn through rubbing action, a tendency to form laps if broken filaments are present, and a high tension required to keep the yarn in the traverse groove.

The object of the present invention is to provide a means by which the very high inertia loads experienced by the cam follower at reversal can be reduced or balanced altogether in a unit traverse mechanism.

Accordingly by our invention we provide a traverse mechanism, for a yarn Winding means, comprising a camoperated reciprocating traverse guide system, characterised in that an elastic diaphragm of low extensibility and low air permeability, which is subject to the pressure of compressed gas on one face and is suitably arranged at each end of the traverse motion substantially in line with the cam follower so that the follower contacts the opposite face of the diaphragm at or near the reversal point of the cam and that the diaphragm absorbs, as potential energy, the kinetic energy of said follower moving in one direction, and returns an appreciable proportion of said energy to the follower as kinetic energy after reversal of the follower direction.

The drawing is an elevational view, partly in section, of a traverse mechanism buffer embodying the principles of the present invention.

That the magnitude of forces involved in reversal of the reciprocating traverse guide system are large, even for systerns weighing only a few ounces, is shown by the following simple calculation.

Assume the traverse speed is 1500 cycles per minute,

the reversal angle of the cam is 20 and the reversal distance is 0.175 inch or 0.0146 foot.

Then the time for reversal is 2 e i500X360 9.002 2 s 0 Therefore the time for the follower to be brought to rest, assuming reversal is symmetrical is 1.11 millisec.

For uniform acceleration, that is parabolic reversal, the acceleration is Thus for a follower of 5 02. weight the reversal force is about 250 lb.

This load, perhaps not high in itself, can be very damaging at high frequencies of the reciprocating parts, particularly if the weight of such parts is increased beyond a few ounces. Furthermore at reciprocating frequencies of this order, rubbing speeds of the cam follower shoe or roller in the cam groove are of the order of several thousand feet per minute, leading to much heat generation when dissipating the reversal forces with consequent reduction in the life of these components.

It is known to balance the reversal forces by such devices as helical springs, as described in British patent specification No. 714,032, and rubber pads arranged to contact the follower at the end of each traverse stroke. However such devices suffer principally from the effects of =23,700 fn/sec. (=738 g.)

. shock loads due to the mass of the spring or rubber buffer and also to the effects of resonance, such that edective buffering takes place only at certain speeds dependent upon the natural vibration frequencies of the buffer and its mass distribution.

The inflated diaphragm of our invention is quite free of such defects, because the material weight of the diaphragm is such that when the follower makes contact with it, the extremely small mass of the diaphragm that moves does not introduce shock loads in the system.

in particular it is possible to adjust the pressure of gas behind and hence the response ofthe inflated diaphragm to the dynamic load applied by contact with the follower so that the load is substantially completely balanced throughout reversal of the follower.

Suitable material for constructing the diaphragm should be light, strong and of high flexibility and low gas perme ability. We have found that synthetic rubber impregnated sail cloth materials made from woven polyester or polyamide fabrics are very suitable. We have also found that it is advantageous to clamp the diaphragm, which may be composed of several layers of the rubber impregnated fabric, under a plate having a hole of suitable diameter in the centre and to mount the whole so that the exposed approximately spherical portion of the pressurised diaphragm protrudes through the clamping plate by a distance equal to or greater than the follower reversal distance.

By' means of such a clamping arrangement changing of the diaphragm is greatly facilitated. We have found that a sandwich comprising a woven fabric centre layer of high tear strength, as for example one woven from high tenacity polypropylene filament yarn, between two layers of a film of high wear resistance, as for example the material Prescollan (registered trademark of the John Bull Rubber Co. Ltd.) which is a thin polyurethane rubber film clamped in this way gives a diaphragm of extremely long life. I

We prefer to form the follower so that the two faces at each end making contact with the diaphragm are flat (or very slightly convex) and circular and have an area adjustment is preferably carried out with an accuracy of i5 lb./sq. inch.- It is alsopossible to vary the characteristics of the buffer by adjusting the volumn of gas under pressure on one side of the diaphragm.

In high speed yarn winding proportionally high traverse speeds are required and an accelerated reversal form of guide motion is particularly necessary, due to the effect of uncontrolled length. Uncontrolled length is the length of yarn between the thread guide and the next point of contact with the drive roll or package surface. For practical reasons it is difficult to reduce the uncontrolled length below a certain value which we have found to be about one inch. At very high wind up speeds with a symmetrical reversal of the thread guide, poor, uneven build of the package will result due to the finite uncontrolled length. If however the thread guide immediately after reversal of direction, is accelerated at a greater rate than it was decelerated before reversal then the build of yarn at high speed is greatly improved. Such an unsymmetrical reversal of the thread guide motion, which we traversing mechanism including a yarn guide assembly 9 which reciprocates between two buffers 12, 14 located at the ends of the path of the mechanism. Each of the buffers includes an elastic diaphragm 16 clamped to a hollow body member 18 by means of an apertured plate 20 through which a substantially spherical portion of the diaphragm protrudes. Gas under pressure is delivered at 22 to the interior of the body 18 and thereby to the side of the diaphragm 16 opposite the guide assembly 9. Oppositely extending end portions 23 .are provided on the guide assembly 9 for engaging the diaphragms 16 at the ends of the traverse path.

The guide assembly 9, whichincludes a yarn guide 1.1 is traversed by means of a cylindrical cam 24 which is rotated about its horizontal axis. A groove 26 in the periphery of the cam 24 receives a cam follower 28 carried by the guide assembly 9.

In one preferred embodiment of our invention a unit traverse mechanism Was constructed having a one ounce follower operating against elastic membranes of Terylene (registered trademark) sail cloth fabric: coated with synthetic rubber. The membranes were inflated with air to a pressure of 65 lb./ sq. inch and maintained at 60-70 lb./sq. inch during continuous operation for 30' hours at a traverse speed of 900 cycles per minute. No fault developed during this period of continuous running.

' In another preferred embodiment of our invention a similar unit traverse mechanism, having a half-ounce follower, was operated. continuously at 1500 cycles per minute during 700 hours against sandwic diaphragms comprising a layer of polypropylene fabric of 4 /2 oz. weight between two layers of Prescollan polyurethane rubberfilm. The follower surfaces in contact with the 0.75 diameter diaphragm were slightly convex (approx. 1" radius of curvature) and 0.5" diameter and the initial air pressure (i.e. when not compressed by contact with the follower) was 60 lb. per sq. inch. Again troublefree operation during the whole period of test was obtained. V a

What we claim is: V 1

1. In a traverse mechanism for yarn winding apparatus of the type including a rotatable cylindrical cam having a groove in the periphery thereof, a cam follower riding in the groove and movable back and forth along a path substantially parallel to the axis of the cam upon rotation thereof; and a yarn guide carried by said cam follower, the improvement which comprises: buffer means at each end of the path of said cam follower for absorbing, as potential energy, the kinetic energy of said cam follower when moving toward said means and for returning an appreciable proportion of said energy to cluding an elastic diaphragm of low extensibility and low air permeability disposed substantially in line with the path of movement of said cam follower so that said cam follower contacts one surface of said diaphragm at about the point at which movement of said cam follower reverses; and means subjecting the other surface of said diaphragm to compressed gas pressure.

2. Apparatus as in claim 1 wherein said buffer means further includes a body member. and a plate. havinga hole therethrough, said elastic diaphragm being clamped between said body member and said plate and an approximately spherical portion of said elastic diaphragm protruding through said hole a distance at least equal to the reversal distance of said cam follower.

3; Apparatus as in claim 1 wherein saidelastic diaphragm is composed of at least one layer of synthetic rubber sail cloth.

4. Apparatus as in claim 1 wherein said elastic diaphragm is of sandwich construction comprising a woven fabric center layer of high tear strength material between two layers of high wear resistant material.

References Cited by the Examiner UNETED STATES PATENTS MERVIN STEIN, Primary Examiner. 

1. IN A TRAVERSE MECHANISM FOR YARN WINDING APPARATUS OF THE TYPE INCLUDING A ROTATABLE CYLINDRICAL CAM HAVING A GROOVE IN THE PERIPHERY THEREOF, A CAM FOLLOWER RIDING IN THE GROOVE AND MOVABLE BACK AND FORTH ALONG A PATH SUBSTANTIALLY PARALLEL TO THE AXIS OF THE CAM UPON ROTATION THEREOF; AND A YARN GUIDE CARRIED BY SAID CAM FOLLOWER, THE IMPROVEMENT WHICH COMPRISES: BUFFER MEANS AT EACH END OF THE PATH OF SAID CAM FOLLOWER FOR ABSORBING, AS POTENTIAL ENERGY, THE KINETIC ENERGY OF SAID CAM FOLLOWER WHEN MOVING TOWARD SAID MEANS AND FOR RETURNING AN APPRECIABLE PROPORTION OF SAID ENERGY TO SAID FOLLOWERR AS KINETIC ENERGY AFTER REVERSAL OF THE MOVEMENT OF SAID CAM FOLLOWER, EACH OF SAID BUFFER MEANS INCLUDING AN ELASTIC DIAPHRAGM OF LOW EXTENSIBILITY AND LOW AIR PERMEABLILITY DIPOSED SUBSTANTIALLY IN LINE WITH THE PATH OF MOVEMENT OF SAID CAM FOLLOWER SO THAT SAID CAM FOLLOWER CONTACTS ONE SURFACE OF SAID DIAPHRAGM AT ABOUT THE POINT AT WHICH MOVEMENT OF SAID CAM FOLLOWER REVERSES; AND MEANS SUBJECTING THE OTHER SURFACE OF SAID DIAPHRAGEM TO COMPRESSED GAS PRESSURE. 